31.Either you or on of your students________to attend the meeting that is due tomorrow.
With the rapid development of the Internet, _______ communication is done by regular mail.
The child should be punished. You shouldn’t let him _____ telling lies.
So amused _______ that I couldn’t help laughing when I saw the children dressed up as Santa Clauses on Christmas Day.
—Who knocked at the door?—I’ve no idea. I just pretended nobody was at home, so I didn’t ask who ____ was.
Glad to see you back. How long _______ in Russia?